Sean McCann finished eighth as he recorded a time of 3:53.47 at Tollcross International Swimming Centre in Glasgow.
He reached the final after qualifying in the same spot.
The 21-year-old, who studies chemical engineering at Loughborough University, previously represented Scotland at the Commonwealth Youth Games in Tobago in 2023, where he finished fifth in the 400m freestyle event.
McCann was swimming from an early age and, while at the City of Leicester club, he won multiple county titles and was national champion in his age group.
Although he grew up in England, he qualifies to swim for Scotland through his father, Gerry, who was born in Glasgow.
His sister Amelie is a promising Scottish triathlete.
McCann is also expected to compete in the men’s 800m and 1,500m freestyle events later in the Commonwealth Games.
He says he hopes to use his experience at the championships to target a place in the Great Britain team for the Los Angeles Olympics in 2028.
McCann was two years old when Madeleine disappeared shortly before her fourth birthday during a holiday in the Portuguese coastal town of Praia da Luz in 2007.
Despite many searches, she has never been found.
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